Metaphyseal-diaphyseal angle (of Drennan) (18-24 months):

A: Line along the lateral tibial cortex

B: Line perpendicular to A at the epiphysis

C: Transverse through the epiphysis

>11 degrees --> Blount disease

>16 degrees --> Greater specificity

Other features:  angulation under the posterior medial epiphysis, metaphyseal irregularity, proximal tibial beaking, epiphyiseal wedging

Staged using the Langenskiold staging system